Controlling and managing authorized access to key assets grows increasingly complex. The various authentication methods that are already known include tamper-resistant key rings; serial numbers on keys; PINs to gain access to keys; locked storage boxes for keys; biometric identifiers of people authorized to access keys; control keys that must be used to gain access to asset keys; and computer systems to monitor and use all these authentication possibilities. There remains a continuing evolution to make key authentication systems more secure against ever more sophisticated assaults on their vulnerabilities.